Though some may use the word apostle in English today to refer to very effective church planters or evangelists, it seems inappropriate and unhelpful to do so, for it simply confuses people who read the New Testament and see the high authority that is attributed to the office of “apostle” there. It is noteworthy that no major leader in the history of the church–not Athanasius or Augustine, not Luther or Calvin, not Wesley or Whitefield–has taken to himself the title of “apostle” or let himself be called an apostle. If any in modern times want to take the title “apostle” to themselves, they immediately raise the suspicion that they may be motivated by inappropriate pride and desires for self-exaltation, along with excessive ambition and a desire for much more authority in the church than any one person should rightfully have.
–Wayne Grudem, Systematic Theology (Church Government, pg. 911)